Advances in video technology are being incorporated into today's healthcare practices. Various types of endoscopes (a flexible tube with a tiny video camera at the tip) are used for colonoscopy, upper gastrointestinal endoscopy, enteroscopy, bronchoscopy, cystoscopy, laparoscopy, wireless capsule endoscopy, and invasive surgeries (e.g., laparoscopic surgery, arthroscopic surgery, video endoscopic neurosurgery). During an endoscopic procedure, an endoscopist advances the endoscope through the patient's anatomy. The tiny video camera generates a video signal of the interior of a human organ, which is displayed on a monitor for real-time analysis by the physician.
Colonoscopy is an important screening tool for colorectal cancer. In the US, colorectal cancer is the second leading cause of all cancer deaths behind lung cancer. As the name implies, colorectal cancers are malignant tumors that develop in the colon and rectum. The survival rate is higher if the cancer is found and treated early before metastasis to lymph nodes or other organs occurs.
The colon is a hollow, muscular tube or lumen about 6 feet long, and consists of six parts or segments: cecum with appendix, ascending colon, transverse colon, descending colon, sigmoid and rectum. Colonoscopy allows for inspection of the entire colon and provides the ability to perform a number of therapeutic operations such as biopsy and polyp removal during a single procedure. A colonoscopic procedure consists of two phases: an insertion phase and a withdrawal phase. During the insertion phase, a flexible endoscope is advanced under direct vision via the anus into the rectum and then gradually into the most proximal part of the colon or the terminal ileum. In the withdrawal phase, the endoscope is gradually withdrawn while the endoscopist moves the camera back and forth to examine suspicious regions. The purpose of the insertion phase is to reach the cecum or the terminal ileum. Careful mucosa inspection and diagnostic or therapeutic interventions such as biopsy, polyp removal, etc., are performed in the withdrawal phase.
Although colonoscopy has become the preferred screening modality for prevention of colorectal cancer, recent data suggest that there is a significant miss-rate for the detection of even large polyps and cancers. The miss-rate may be related to the quality of the video image produced during the procedure that is then reviewed by the physician or endoscopist. Current endoscopes are equipped with a single, wide-angle lens, and typically do not have camera operation function such as zoom-in, zoom-out and auto focusing. Thus, video data of colonoscopies typically have many blurry (out-of-focus) frames due to frequent shifts of camera positions while moving along the colon. Because of these limitations, a significant number of out-of-focus frames (for colonoscopy the average is about 37%, but it can be over 60% depending on the endoscopist's skill and the patient's conditions) are included in the colonoscopy video. The out-of-focus frames do not hold any useful information. Such out-of-focus or non-informative frames are usually generated for the following reasons: (1) too-close (or too-far) focus into (from) the mucosa of the colon or (2) foreign substances (i.e., stool, cleansing agent, air bubbles, etc.) covering camera lens.
In addition, non-informative frames may be caused by the endoscope camera moving too rapidly through the colon. Thus, the miss-rate, or the ability to review the endoscopy video efficiently and accurately, is related to the experience of the endoscopist in generating the endoscopy video. This is because it is the endoscopist who controls the speed of the camera's movement through the colon and when and how often the camera is moved back and forth.
In one example, current American Society for Gastrointestinal Endoscopy guidelines suggest that on average the withdrawal phase during a screening colonoscopy should last a minimum of 6-10 minutes. However, even though the withdrawal time may meet the guidelines, the quality of the colonoscopy cannot be determined if the colonoscopic procedure has a large number of out-of-focus frames in the withdrawal phase, or if a relatively low number of frames are devoted to suspicious regions. Currently, there is no measurement method to evaluate the endoscopist's skill and the quality of colonoscopic procedure.
What is needed, then, is a method of analyzing an endoscopy video to evaluate the endoscopist's skill and the quality of the endoscopy procedure.